PHP的观察者设计模式实现相对简单，但是PHP5+版本中已经有标准库类库支持，我们只需简单继承并实现就可以了。

观察者：实现标准接口类库SplSubject。一个注册方法：attach，一个取消注册方法：detach。一个通知方法：nofity。

<?php

class TSPLSubject implements SplSubject{

	 private $observers, $value;

	 public function __construct(){
		$this->observers =array();
	 }

	 public function attach(SplObserver $observer){
		$this->observers[] = $observer;
	 }

	 public function detach(SplObserver $observer){
		if($idx = array_search($observer, $this->observers,true)) {
			unset($this->observers[$idx]);
		}
	 }
	 
    /**
	 *
	 * Notify observers one by one (main entry)
	 *
	 * @param none
	 * @return none
	 */
	 public function notify(){
		foreach($this->observers as $observer){
			$observer->update($this);
		}
	 }

	 public function setValue($value){
		$this->value = http://www.mamicode.com/$value;>
被观察者：实现标准接口类库SplObserver。一个update方法。
<?php

class TSPLObserver implements SplObserver{
	 public function update(SplSubject $subject){
		 echo 'The new state of subject ' , nl2br("\r\n");
//		 echo 'The new state of subject '.$subject->getValue();
	 }
}
<?php

class TSPLObserver1 implements SplObserver{
	 public function update(SplSubject $subject){
		 echo 'The new state of subject one ' , nl2br("\r\n");
//		 echo 'The new state of subject '.$subject->getValue();
	 }
}


测试调用（同目录下）：
<?php

function __autoload($classname) { 
  require_once ($classname . ".php"); 
}

$subject = new TSPLSubject();
$subject->attach(new TSPLObserver());
$observer1 = new TSPLObserver1();
$subject->attach($observer1);
//$subject->attach(new TSPLObserver2());
//$subject->detach($observer1);

$subject->notify();

exit();

输出：
>php basic.php
The new state of subject <br />
The new state of subject one <br />
PHP5+标准函数库观察者之实现